This invention relates to motor-driven gear trains and, more particularly, to a self-adjusting motor mount for holding a driving gear mounted on the shaft of a motor in engagement with a driven gear carried by a back plate disposed in a vertical plane comprising, a mounting plate carrying the motor and the driving gear; pivotal mounting means carried by the back plate for attaching the mounting plate to the back plate at a point above the motor for pivotal movement therearound so as to have the motor pivotally hang from the point; bias means for resiliently urging the mounting plate to carry the driving gear into engagement with the driven gear; and, shock absorber means carried by the back plate for absorbing pivotal gear disengaging movement of the mounting plate.
There are many applications in which a driving gear on the shaft of a driving motor is mounted to engage a driven gear. In most such applications, the motor is simply bolted in place adjacent the driven gear and the two gears mesh sufficiently for the intended purpose. Where finer adjustment is desired, the approach of FIGS. 1 and 2 is commonly employed. The motor 10 is attached to a mounting plate 12. One side of the mounting plate 12 has a first projecting tab 14 having a hole therethrough through which a first mounting screw 16 passes into threaded engagement with the back plate 18 which carries the entire assembly. Thus, the mounting plate 12 is free to pivot about the screw 16. The other side of the mounting plate 12 has a second projecting tab 20 having a slot 22 therethrough through which a second mounting screw 24 passes into threaded engagement with the back plate 18. To assemble the parts, the mounting plate 12 is loosely attached to the back plate 18 with the mounting screws 16, 24 and pivoted about the first mounting screw 16 until the driven gear 26 and drivig gear 28 are properly meshed. The two mounting screws 16, 24 are then tightened to hold everything in place.
Most precision equipment as wherein the above-described prior art mounting approach is applied is of a small size such that there are very little, if any, shock forces on the mounting structure. Also, there is very little wear in the parts which can cause problems. By contrast, a pen plotter is quite large with correspondingly large parts. On the other hand, it is by necessity a precision instrument in every sense of the word. When the above-described prior art motor mounting system is employed to mount the motors driving the driving drum and the plotting head, shocks of moving the plotter during initial delivery or subsequent relocation can move the driving and driven gears 28, 26 out of alignment. Moreover, pressures of use can cause wear and uneven wear in the gears 28, 26 causing "jitter", which can effect the plot quality, and audible noise, which is simply annoying. The inability to provide close gear contact or non-parallel alignment of the gears 28, 26 can also result in backlash, and the like, which effects plot quality.
Wherefore, it is an object of this invention to provide a motor mount for use in gear drives of large precision instruments such as pen plotters and the like which is self-adjusting so as to automatically compensate for shock movement and wear in the gears and environmental changes that could cause uncoupling of the mating gears.
It is another object of this invention to provide a motor mount for use in gear drives of large precision instruments such as pen plotters and the like in which driving gears and driven gears are kept in a parallel orientation with one another.
It is still another object of this invention to provide a motor mount for use in gear drives of large precision instruments such as pen plotters and the like in which driving gears and driven gears are kept in optimum engagement so as to reduce or eliminate backlash.
Other objects and benefits of the invention will become apparent from the detailed description which follows hereinafter when taken in conjunction with the drawing figures which accompany it.